Richtek RT8452GQW, RT8452GS Schematic [ru]

Conceptual

RT8452

High Voltage High Current LED Driver Controller for Boost
or Buck-Boost Topology

General Description

The RT8452 is a current mode PWM controller designed
to drive an external MOSFET for high current LED
applications. With a current sense amplifier threshold of
180mV, the LED current is programmable with one
external current sense resistor and the power loss is
minimized. With the maximum operating input voltage of
40V and output voltage up to 60V, the RT8452 is ideal for
boost or buck-boost operation. (See RT8450 and RT8451
for buck mode LED driver application.)

With 1MHz operating frequency, the external inductor and
capacitors can be small while mainteining high efficiency.

Dimming can be either analog or PWM digital. The unique
built-in clampping comparator and filter allow easy low
noise analog dimming conversion from PWM signal with
only one external capacitor. PWM dimming control is made
easy with a build in FET driver dedicated for the extermal
dimming MOSFET.

The RT8452 is available in WQFN-16L 3x3 and SOP-16

packages.

Features

l High Voltage Capability : V

60V

l Boost or Buck-Boost Operation
l Current Mode PWM with 1MHz Switching

Frenquency

l Easy Dimming : Analog, PWM Digital or PWM

Converting to Analog with One External Capacitor

l Programmable Soft Start to Avoid Inrush Current
l Programmable Over Voltage Protection to Limit

Output Voltage

l V

Undervoltage Lockout and Thermal Shutdown

IN

l 16-Lead WDFN and SOP Packages.
l RoHS Compliant and 100% Lead (Pb)-Free

Up to 40V, V

IN

OUT

Up to

Applications

l General Industrial High Power LED Lighting
l Desk Lights and Room Lighting
l Building and Street Lighting
l Industrial Display Backlight

Ordering Information

RT8452

Package Type

S : SOP-16

QW : WDFN-16L 3x3 (W-Type)
Operating Temperature Range

G : Green (Halogen Free with Commer­ cial Standard)

Note :
Richtek Green products are :

}RoHS compliant and compatible with the current require-

ments of IPC/JEDEC J-STD-020.

}Suitable for use in SnPb or Pb-free soldering processes.
}100% matte tin (Sn) plating.

Marking Information

For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.

Pin Configurations

(TOP VIEW)

GND

VCCENOVP

GBIAS

PWMOUT

PWMOUT

PWMDIM

1
2

GATE

ISW

GND

3
4

ISP

PWMDIM

WQFN-16L 3x3

GBIAS

GATE

ISW

ISP
ISN

2
3
4
5
6
7

VCACTL

SOP-16

13141516

12

NC

11

SS

10

DCTL

17

9

ACTL

8765

VC

ISN

16

GND

15

VCC

14

OVP

13

EN

12

NC

11

SS

10

DCTL

98

DS8452-02C March 2008www.richtek.com

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RT8452

Typical Application Circuit

V

Analog

Dimming

R1

10k

C2
3nF

R1

10k

C2
3nF

IN

5V

C3
10nF

Figure 1. Analog Dimming in Boost Configuration

V

IN

5V

C3
10nF

C4

4.5V to 40V

4.5V to 40V

PWM
Dimming control

C1

15
13

10

11

C4

C1

C5

0.5uF

9

8

1

15
13

10

8

11

1

9

Conceptual

L

10uH

RT8452

VCC
EN

ACTL
DCTL

VC
SS

GBIAS

VCC
EN

DCTL

VC
SS

GBIAS
ACTL

PWMOUT

PWMDIM

GND

L

10uH

RT8452

PWMOUT

PWMDIM

GND

2

GATE

4

ISW

6

ISP

7

ISN

14

OVP

3
5

16, Exposed Pad (17)

2

GATE

4

ISW

6

ISP

7

ISN

14

OVP

3
5

16, Exposed Pad (17)

R3

R3

C5
1uF

R5

C6
1uF

R5

R4

R4

R2

180mV

R2

180mV

V

V

OUT

OUT

V

OUT

60V MAX

V

OUT

60V MAX

Figure 2. PWM to Analog Dimming in Boost Configuration

V

OUT

V

4.5V to 40V

R1

10k

C2
3nF

5V

L

VCC
EN

ACTL
DCTL
VC

SS
GBIAS

10uH

RT8452

GATE

ISW

ISP

ISN

PWMOUT

PWMDIM

OVP

GND

16, Exposed Pad (17)

14

2
4

6
7
3

5

R3

IN

C1

15
13

9

10

8

11

C3
10nF

1

C4

C5
1uF

R5

180mV

R4

R2

V

OUT

60V MAX

Figure 3. True PWM Dimming in Boost Configuration

DS8452-02C March 2008www.richtek.com

2

Sense Pin. Connect the current

V

4.5V to 40V

IN

5V

Analog

Dimming

R1

10k

C2
3nF

C3
10nF

C1

C4

Figure 4. Analog Dimming in Buck-Boost Configuration

Functional Pin Description

15
13

9

10

8

11

1

Conceptual

RT8452

VCC
EN

ACTL
DCTL

VC
SS

GBIAS

PWMOUT

PWMDIM

GND

L

10uH

2

GATE

4

ISW

7

ISN

6

ISP

3
5
14

OVP

16, Exposed Pad (17)

R3

R5

R4

C5
1uF

R2

180mV

V

OUT

V

OUT

60V MAX

RT8452

SOP-16 QFN3X3-16 Pin Name

Pin Function

1 1 GBIAS The Internal Gate Driver Bias Pin.A good bypass capacitor is required.
2 2 GATE The External MOSFET Switch Gate Driver Output Pin.
3 3 PWMOUT The Output Pin for the PWM Dimming FET Driver.

4 4 ISW

The External MOSFET Switch Current

sense resistor between external N-MOSFET switch and the ground.

5 5 PWMDIM The Control Input Pin for the PWM Dimming FET Driver.
6 6 ISP The LED Current Sense Amplifier Positive Input.

7 7 ISN

The LED Current Sense Amplifier Negative Input. Voltage

threshold between ISP and ISN is 180mV.

8 8 VC The PWM Control Loop Compensation Pin.
9 9 ACTL

The Analog Dimming Control Pin. The effective programming

voltage range of the pin is between 0.3V and 1.2V.

By adding a 0.1uF filtering capacitor on ACTL pin, the PWM dimming

10 10 DCTL

11 11 SS

signal on DCTL pin can be averaged and converted into analog

dimming signal on the ACTL pin following the formula below.

V

= 1.2V x PWM Dimming Duty Cycle.

ACTL

The Soft-Start Pin. A capacitor of at least 10nF is required for proper

soft start.

12 12 NC No Internal Connection.
13 13 EN

14 14 OVP

The Chip Enable (Active High) Pin. When this pin voltage is low, the

chip is in shutdown mode.
The Over Voltage Protection Pin. The PWM converter turns off when
The voltage of the pin goes higher than 1.2V.

15 15 VCC

16

16

Exposed Pad (17)

DS8452-02C March 2008www.richtek.com

GND

The Power Supply Pin of the Chip. For good bypass, a low ESR
Capacitor is required.

The Ground Pin. The exposed pad must be soldered to a large PCB
And connected to GND for maximum power dissipation.

3

RT8452

Function Block Diagram

Conceptual

EN

VCC

OVP

VC

SS

DCTL

1.4V

4.5V

1.2V

1.2V

+

-

6uA

+

-

­+

+

-

Shutdown

-

ACTL

6V

OSC

+

GM

1.2V

+

-

100k

100mV

VCC

GBIAS
GATE

5V

GBIAS

PWMOUT
PWMDIM

ISW
ISN

ISP

GND

+

-

S

R
R
R

R

­+

­+

V

ISP

180

– V

(mV)

0

ISN

0.31.2

Figure 5

V

ACTL

(V)

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Conceptual

Absolute Maximum Ratings (Note 1)

RT8452

l Supply Input Voltage, V
l GBIAS, GATE, PWMDIM, PWMOUT, ISW--------------------------------------------------------------------10V
l ISP, ISN----------------------------------------------------------------------------------------------------------------65V
l DCTL, ACTL, OVP, EN---------------------------------------------------------------------------------------------20V
l Power Dissipation, P

-----------------------------------------------------------------------------------------45V

CC

@ TA = 25°C

D

SOP-16----------------------------------------------------------------------------------------------------------------1.053W

WQFN-16L 3x3--------------------------------------------------------------------------------------------------------1.471W

l Package Thermal Resistance (Note 4)

SOP-16, θJC-----------------------------------------------------------------------------------------------------------95°C/W
SOP-16, θJC----------------------------------------------------------------------------------------------------------45°C/W

WQFN-16L 3x3, θJA-------------------------------------------------------------------------------------------------68°C/W

WQFN-16L 3x3, θJC-------------------------------------------------------------------------------------------------7.5°C/W

l Junction Temperature-----------------------------------------------------------------------------------------------150°C
l Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------260°C
l Storage Temperature Range--------------------------------------------------------------------------------------- −65°C to 150°C
l ESD Susceptibility (Note 2)

HBM (Human Body Mode)-----------------------------------------------------------------------------------------2kV
MM (Machine Mode)------------------------------------------------------------------------------------------------200V

Recommended Operating Conditions (Note 3)

l Junction Temperature Range-------------------------------------------------------------------------------------- −40°C to 125°C
l Ambient Temperature Range-------------------------------------------------------------------------------------- −40°C to 85°C

Electrical Characteristics

(VCC = 24V, No Load on any Output, T

Parameter Symbol Conditions Min Typ Max Unit

Overall

Supply Voltage V
Supply Current I

Shutdown Current I
Shutdown Threshold V

EN Input Current V

Current Sense Amplifier

Input Threshold (V

ISP

− V

) 4.5V ≤ common mode ≤ 40V 170 180 190 mV

ISN

ISP / ISN Input Current I
VC Output Current I
VC Threshold for PWM Switch

Off

LED Dimming

= 25°C, unless otherwise specified)

A

4.5 -- 40 V

CC

VC ≤ 0.4V (Switching off) -- 4 6 mA

VCC

VEN ≤ 0.7V -- 12 -- uA

SHDN

-- 1.4 -- V

EN

≤ 5V -- -- 0.5 uA

EN

/ I

ISP

VC

ISN

4.5V ≤ V
V

− V

ISP

0.5V ≤ VC ≤ 2.4V

= V

ISP

= 120mV,

ISN

≤ 60V -- 140 -- uA

ISN

-- ±20 -- uA

-- 0.7 -- V

Analog Dimming ACTL Pin
Input Current

DS8452-02C March 2008www.richtek.com

I

0.3V ≤ V

ACTL

≤ 1.3V -- -- 1 uA

ACTL

To be continued

5

RT8452

Parameter Symbol Conditions Min Typ Max Unit

Conceptual

LED Current Off Threshold at
ACTL
DCTL Input Current I

V

ACTL_Off

0.3V ≤ V

DCTL

-- 0.2 -- V
≤ 6V -- -- 0.5 uA

DCTL

PWM Control

Switching Frequency f
Maximum Duty Cycle
(Note 5)

800k

SW

1M 1.2M

Hz

-- 86 -- %

Minimum on Time -- 200 -- ns

Switch Gate Driver

GBIAS Voltage V
Gate Voltage High V

Gate Voltage Low V

GBIAS

Gate_H

Gate_L

I

GBIAS

I

Gate

I

Gate

I

Gate

I

Gate

= 20mA -- 5.7 -- V
= −50mA -- 4.2 -­= −100uA -- 5 -­= 50mA -- 0.25

--

= 100uA -- 0.1 --

V

V

GATE Drive Rise and Fall Time 1nF Load -- 15 -- ns
PWM Switch Current Limit
Threshold

I

SW_LIM

-- 100 -- mV

PWM Dimming Gate Driver

PWMDIM Threshold (Low to
High)

-- 1.5 -- V

PWMDIM Threshold Hysteresis -- 0.5 -- V
PWMOUT Drive Rise and Fall
Time

1nF Load -- 40 -- ns

OVP and Soft Start

OVP Threshold V
OVP Input Current I
Soft Start Pin Current I

Note 1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.

These are stress ratings only, and functional operation of the device at these or any other conditions beyond those
indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.

Note 2. Devices are ESD sensitive. Handling precaution recommended. The human body model is a 100pF capacitor discharged

through a 1.5kΩ resistor into each pin.

Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of

JEDEC 51-7 thermal measurement standard.

Note 5. When the natural maximum duty cycle of 1MHz switching frequency is reached, the switching cycle will be skipped (not

reset) as the operating condition requires to effectively stretch and achieve higher on cycle than the natural maximum
duty cycle set by the 1MHz switching frequency.

OVP
SS

-- 1.2 -- V

OVP_th

0.7V ≤ V

V

≤ 2V -- 6 -- uA

SS

≤ 1.5V -- -- 0.1 uA

OVP

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Datasheet Revision History

Conceptual

RT8452

Version

00C 2008/2/22 first edition

01C 2008/2/27

02C 2008/3/18 Ordering Information Modify

Data Page No.

Item Description

Features
Typical Application Circuit
Functional Pin Description
Function Block Diagram
Electrical Characteristics

Modify

DS8452-02C March 2008www.richtek.com

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RT8452

Outline Dimension

Conceptual

D

E

A

A3

A1

Symbol

A 0.700 0.800 0.028 0.031

Dimensions In Millimeters

D2

Min Max Min Max

SEE DETAIL A

1

E2

be

L

1
2

1
2

DETAIL A

Pin #1 ID and Tie Bar Mark Options

Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.

Dimensions In Inches

A1 0.000 0.050 0.000 0.002
A3 0.175 0.250 0.007 0.010

b 0.180 0.300 0.007 0.012

D 2.950 3.050 0.116 0.120

D2 1.300 1.750 0.051 0.069

E 2.950 3.050 0.116 0.120

E2 1.300 1.750 0.051 0.069

e 0.500 0.020
L 0.350 0.450

0.014 0.018

W-Type 16L QFN 3x3 Package

DS8452-03C December 2008www.richtek.com

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Conceptual

RT8452

J

I

Symbol

A

F

D

Dimensions In Millimeters

B

C

Dimensions In Inches

H

Min Max Min Max

M

A 9.804 10.008 0.386 0.394
B 3.810 3.988 0.150 0.157
C 1.346 1.753 0.053 0.069
D 0.330 0.508 0.013 0.020
F 1.194 1.346 0.047 0.053
H 0.178 0.254 0.007 0.010

I 0.102 0.254 0.004 0.010
J 5.791 6.198 0.228 0.244

M 0.406 1.270 0.016 0.050

Richtek Technology Corporation

Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: [phone] Fax: [phone]

16–Lead SOP Plastic Package

Richtek Technology Corporation

Taipei Office (Marketing)
8F, No. 137, Lane 235, Paochiao Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: [phone] Fax: [phone]
Email: [e-mail]

Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design,
specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed
by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.

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